Coupler plugs are usually configured for the connection between a cable harness plug and a lambda probe, the connectors in the coupler plug being provided for balancing, signaling, and/or heating of the probe. The lambda probe and lambda closed loop control represent an effective exhaust gas cleaning method in conjunction with the three-way catalyst. The lambda probe, which, for example, is screwed into an exhaust gas system, includes a measuring sensor for determining the oxygen concentration of the exhaust gas.
The residual oxygen content is very suitable as a measured variable and regulates the air/fuel ratio, since it accurately indicates whether the air/fuel mixture is combusting completely.
In this regard, the lambda probe delivers a voltage signal which represents the momentary value of the mixture's composition and tracks changes in the mixture. The fuel supply to the engine is regulated by a mixture formation system in accordance with the signal from the lambda probe in such a way that a stoichiometric air-fuel ratio λ=1 will be achieved. Heated or unheated probes are utilized, depending on the design of the exhaust gas system and the operating conditions. The lambda probe has other uses apart from motor vehicles, e.g., for regulating gas motors or oil/gas burners in heating systems.
Broad-band lambda probes, in particular, are constructed in a modular way, and permit the integration of several functions in connection with planar technology. They usually have functional layers, which are made up of a porous protective layer, an external electrode, a sensor foil, an internal electrode, a reference air channel foil, an insulation layer, a heating element, a heating foil, a resistor or a balancing element, and terminal contacts.
Since the broad-band lambda probe is made up of the combination of a Nernst concentration cell (=sensor cell) with an oxygen ion-transporting pump cell, it can measure very accurately not only at the stoichiometric point where lambda=1, but also in the lean and the rich range.
Each probe has to be adjusted individually. For this, the probe has a built-in resistor (mini-hybrid). The adjustment, which is preferably made with the aid of a laser beam, is done in such a way that the resistor layer, which is on a ceramic substrate, is correspondingly removed, whereby a change in resistance is brought on, which results in an adjustment.
One specific embodiment is seen in the fact that the balancing unit, or the resistor, is arranged right on the probe. A further exemplary embodiment is seen in the fact that the resistor is accommodated outside, for example on a cable harness plug that is coupled to the probe.
To prevent moisture, dirt or similar substances from penetrating the coupler plug in which the corresponding lambda probe is arranged as well, and to ensure that the corresponding atmosphere prevails inside the coupler plug, the coupler plug has sealing elements, which are arranged on the cover element, for instance, or on additionally provided pressure-equalizing elements.
Coupler elements of the aforementioned type may be embodied in various forms. They are generally multi-pin coupler plugs, which have corresponding flat plug-connectors.
Other designs have flat plug-connectors exclusively.
Some other designs have combinations of flat plug-connectors and flat contacts.
In particular when using coupler plugs that have multiple poles and accommodate flat contacts and simultaneously also flat connectors in one coupler plug, it is provided to make available at least one secondary locking mechanism in the flat plug-connector region so as to fixate the flat contacts disposed in the housing, and to additionally include a further secondary locking mechanism for the flat contacts so as to fixate them in the housing in a corresponding manner as well.
One disadvantage of the last mentioned specific embodiment of coupler plugs is that it requires additional work and installation steps to implement a corresponding fixation by means of a secondary locking mechanism both of flat plug-connectors and flat contacts. In addition, multiple controls are necessary in order to ascertain whether the fixation of the flat plug-connectors or the flat contacts has been accomplished successfully.